Introduction
Upright sitting in a wheelchair is important to reduce pressure on the sacrum and coccyx, it aids in better breathing, increases head control, increases stability and improves independence. A good wheelchair cushion creates a levelled sitting surface, reduces risk of skin breakdown, and limits sliding and slouching.1
A study was designed in order to test the resistance of different wheelchair cushions against sliding of the user in a laboratory environment. Creeping of the pelvis forward due to gravity and creating posterior pelvic tilt is also studied.
Method
A skinny indenter is placed on different cushions, 30kg is placed on the indenter to simulate the weight of the upper body. The indenter is horizontally pulled forward. A Force Gauge (PCE-FM 0.5-500N) measures the force that is needed to displace the indenter 4cm (dynamic force).
The test on each cushion is repeated three times, to ensure repeatability. Five different cushions are tested, of which three Vicair cushions, namely: Adjuster O2 (10cm thickness, Comfair cover), Vector O2 (10cm thickness, Comfair cover), and the Active O2 (9cm thickness). The other cushions that were tested are a ROHO Quadtro select high profile (locked) and a Jay J3. The Vicair Vector O2 is tested directly out of the box and set-up for optimal immersion (2.5cm below the indenter).
Results
R&D
Literature Review: Pelvic obliquity
Because in a wheelchair the backsupport gives resistance
The maximum force measured is the resistance that the cushion gives against the indenter to prevent sliding. This is the most relevant measurement because this force is the resistance the cushion can give the user to sit stable. The maximum force ranges from 100N for a Jay J3 to 176N for a Vicair Vector O2.
The Jay J3 cushion, a foam cushion with fluid inlay, gives the least resistance against slouching, with a mean of 106N, followed by the Vicair Active O2, with a mean of 137N. The out of the box Vicair Vector O2 performs almost the same as the ROHO Quadtro Select, 148.2N vs 147.8N. But when the Vicair Vector is set up for the indenter it outperforms all the other cushions, with a mean force of 172N. The out of the box Vicair Adjuster O2 also performs good with a mean resistance of 166N.
Discussion
The results do not only represent the force that is needed for sliding, but can also be extrapolated to resistance to pelvic tilt.
Because in a wheelchair the backsupport gives resistance
The maximum force measured is the resistance that the cushion gives against the indenter to prevent sliding. This is the most relevant measurement because this force is the resistance the cushion can give the user to sit stable. The maximum force ranges from 100N for a Jay J3 to 176N for a Vicair Vector O2.
The Jay J3 cushion, a foam cushion with fluid inlay, gives the least resistance against slouching, with a mean of 106N, followed by the Vicair Active O2, with a mean of 137N. The out of the box Vicair Vector O2 performs almost the same as the ROHO Quadtro Select, 148.2N vs 147.8N. But when the Vicair Vector is set up for the indenter it outperforms all the other cushions, with a mean force of 172N. The out of the box Vicair Adjuster O2 also performs good with a mean resistance of 166N.
Discussion
The results do not only represent the force that is needed for sliding, but can also be extrapolated to resistance to pelvic tilt.
against pelvic tilt, as a result the user needs to slide over the cushion to slouch and create the pelvic tilt. Which is also visible is figure 1.
Conclusion
Vicair cushions offer very good resistance against sliding and pelvic tilt. Out of the box, the Vicair cushions are already a better choice compared to the tested Jay J3 cushion (30 – 63% better). The Vicair Adjuster O2 is, out of the box, better than the set ROHO Quadtro Select (12% better). When the Vicair Vector O2 is ideally adjusted for the indenter, the positive difference becomes more apparent (16% better, 24N difference).
